android第三次作业

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/tv1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="文本信息"
        android:textColor="#FFF79E38"
        android:textSize="25sp"
        android:gravity="center"
        android:textStyle="italic"/>
    
    
    <EditText
        android:id="@+id/et1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv1"
      />
     <EditText
        android:id="@+id/et2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et1"
         
      />
     
       <TextView
        android:id="@+id/tv2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"  
        android:layout_below="@id/et2" 
        android:text="显示计算结果"
        android:gravity="center"
        android:textStyle="italic"/>
    
     <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/tv1"
        android:text="+"
        android:textColor="#FFF79E38"
        android:textSize="25sp"
        android:gravity="center"
        android:textStyle="italic"   
        android:onClick="click"   
        />
     
       <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/btn1"
        android:text="-"
        android:textColor="#FFF79E38"
        android:textSize="25sp"
        android:gravity="center"
        android:textStyle="italic"   
        android:onClick="click"  
        />


</RelativeLayout>

package com.example.q;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void click(View v) {
        TextView tv2 = (TextView) findViewById(R.id.tv2);
        EditText et1 = (EditText) findViewById(R.id.et1);
        EditText et2 = (EditText) findViewById(R.id.et2);
        
        int num1,num2,result=0;
        num1=Integer.parseInt(et1.getText().toString());
        num2=Integer.parseInt(et2.getText().toString());
        
        switch (v.getId()) {
        case R.id.btn1:
            result=num1+num2;
            break;
        case R.id.btn2:
            result=num1-num2;
            break;
        }
        tv2.setText(result+"");
    }

}